The recent literature discloses a variety of mercaptoacyl amino acids which are useful for inhibiting the conversion of angiotensin I to angiotensin II in mammals, and are, therefore, useful in the treatment of hypertension. U.S. Pat. No. 4,105,776, issued Aug. 8, 1978 discloses mercaptoacyl amino acids wherein the amino acid is, inter alia, proline, 4-hydroxyproline and 4-alkylproline.
U.S. Pat. No. 4,154,935, issued May 15, 1979 discloses mercaptoacyl amino acids wherein the amino acid is, inter alia, 4-halogen substituted proline or 4,4-dehalogen substituted proline.
United Kingdom patent application No. 2,027,025, published Feb. 13, 1980, discloses mercaptoacyl amino acids wherein the amino acid is 5-substituted prolines.
United Kingdom patent application No. 2,028,327, published Mar. 5, 1980, discloses mercaptoacyl amino acids wherein the amino acid is, inter alia, proline substituted in the 3- or 4-position with with a group having the formula R--S-- or R--O-- wherein R is alkyl, alkenyl, alkynyl, phenyl, substituted phenyl, phenylalkyl or substituted phenylalkyl.
U.S. Pat. No. 4,168,267, issued Sept. 18, 1979 discloses phosphinylalkanoyl prolines and esters or salts thereof.
The compounds disclosed by the above mentioned references are disclosed as inhibitors of the action of angiotensin converting enzyme in mammals and as useful hypotensive agents.